Method for applying a security code to an article

ABSTRACT

For applying a security code to an article, such as a cheque guarantee card, credit card, identity card or component of a motor or machine, use is made of a hologram or kinegram wherein personification or identification symbols, letters, numerals or figures are or will be cut out by burning-in using a laser beam, said hologram or kinegram being affixed to an underlying hologram or kinegram which is affixed to the article directly or via one or more holograms or kinegrams, the various features being such that the optical effect of an underlying hologram or kinegram is visible through the cut-out symbols.

The invention relates to a method for applying a security code to anarticle, such as a cheque guarantee card, credit card, identity card orcomponent of a motor or machine, wherein a diffraction-generatingmicrostructure, such as a hologram or kinegram, is applied to saidarticle, in which diffraction-generating microstructure personificationor identification symbols, such as letters, numerals or figures, are cutout by means of burning-in using a laser beam.

BACKGROUND OF THE INVENTION

A relevant example of a method for applying a security code to anarticle is used in the production of the so-called Europass. For thispass the diffraction-generating microstructure consists of a hologramand the cut-out symbols consist of four numerals, which extend throughthe entire depth of the hologram. As a result of the cut-out symbols,all that is seen at these locations is the substrate, that is to say theplastic card, which has been burned black. The possibility of thecut-out symbols being rendered invisible by filling up and of new,different personification or identification symbols being cut out is notexcluded. Counterfeiting is thus possible.

The aim of the invention is, if not to preclude counterfeiting,certainly to make this appreciably more difficult.

SUMMARY OF THE INVENTION

According to the invention said microstructure is glued to anotherunderlying diffraction-generating microstructure such as a hologram orkinegram, which is affixed to the article directly or via one or moreother diffraction-generating microstructures, said symbols being cut outfrom the top diffraction-generating microstructure in such a size sothat the optical effect of the underlying diffraction-generatingmicrostructure becomes visible and/or detectable.

The essential feature for the result is that, in addition to the upperhologram, kinegram or optionally another "optical variable device", anoptical effect of an underlying hologram or kinegram is also visible viathe cut-out symbols. Of course, the principle of the invention is alsoapplicable in the case of more than two holograms or kinegrams glued ontop of one another. With this arrangement, via some cut-out symbols inthe top diffraction-generating microstructure, the optical effect of thediffraction-generating microstructure located beneath it can be seen,whilst via cut-out symbols in the top diffraction-generatingmicrostructure and the diffraction-generating microstructure locatedbeneath it the optical effect of the underlying microstructure can beseen.

The said cut-out symbols can be burned in either after or beforeaffixing the top diffraction-generating microstructure. If the cut-outsymbols are applied after affixing the relevant diffraction-generatingmicrostructure, burning-in must be carried out with the utmost care toprevent damage to the underlying hologram or kinegram.

The invention will now be explained with the aid of the two diagrammaticfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of a plastic card with a security code appliedthereon according to the invention.

FIG. 2 shows a cross-section of the card according to FIG. 1 on a largerscale.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

A first hologram or kinegram 2 has been glued on a plastic card 1, whichserves as substrate, and a second hologram or kinegram 3 has been gluedon to said first hologram or kinegram. In the upper, second hologram orkinegram 3, cut-out symbols 4 in the form of numerals have been made bymeans of a laser beam.

A person looking at the card sees the top hologram or kinegram 3 and,via the cut-out symbols 4, also sees the optical effect of theunderlying hologram or kinegram 2.

The difference between a hologram and a kinegram is that a hologramsuggests depth and a kinegram suggests movement. Both a hologram and akinegram are formed by a diffraction-generating microstructure with areflective coating consisting of a metal alloy.

It is exceptionally difficult, if not virtually impossible, to removethe top hologram or kinegram without damaging the bottom hologram orkinegram, or to fill in the cut-out symbols 4 in the top hologram orkinegram 3 and then to cut out symbols in approximately the sameposition without the optical effect of the bottom hologram or kinegrambeing damaged or substantially changed at the location of the cut-outsymbols. Counterfeiting is therefore not easy to establish because anincomplete or damaged optical effect of the bottom hologram or kinegrambecomes visible via the cut-out symbols in the top hologram or kinegram.

The top hologram or kinegram 3 can be glued to the bottom hologram orkinegram 2 before or after making the cut-out symbols 4.

More than two holograms or kinegrams glued to one another are alsopossible, in which case some cut-out symbols extend only through the tophologram or kinegram and other cut-out symbols extend through severalholograms or kinegrams. Only the bottom hologram or kinegram remainsunaffected.

The invention can be employed not only for cheque guarantee cards andcredit cards but also for identity cards, machine components and thelike. Within the scope of the invention, all sorts of variants are alsoconceivable in respect of the card referred to as an illustrativeembodiment.

I claim:
 1. A method for applying a security code to an article, whereina diffraction-generating microstructure is applied to said article, inwhich diffraction-generating microstructure personification oridentification symbols are cut out by means of burning-in using a laserbeam, wherein the said microstructure defines a top microstructure thatis glued to another underlying diffraction-generating microstructurewhich is affixed to the article directly or via one or more otherdiffraction-generating microstructures, said symbols being cut out fromthe top diffraction-generating microstructure in such a size so that theoptical effect of the underlying diffraction-generating microstructurebecomes visible and/or detectable.
 2. A method according to claim 1wherein the said symbols are made before the top diffraction-generatingmicrostructure is affixed to the underlying diffraction-generatingmicrostructure.
 3. A method according to claim 1, wherein the saidsymbols are burned in by means of laser beams after affixing the topdiffraction-generating microstructure, without the underlyingdiffraction-generating microstructure being damaged.
 4. A methodaccording to claim 1 wherein three or more diffraction-generatingmicrostructures are affixed on top of one another and, through somecut-out symbols in the top diffraction-generating microstructure, theoptical effect of the diffraction-generating microstructure locatedbeneath it can be seen, and via cut-out symbols in the topdiffraction-generating microstructure and the diffraction-generatingmicrostructure located beneath it the optical effect of the underlyingdiffraction-generating microstructure can be seen.
 5. A method accordingto claim 2 wherein three or more diffraction-generating microstructuresare affixed on top of one another and, through some cut-out symbols inthe top diffraction-generating microstructure, the optical effect of thediffraction-generating microstructure located beneath it can be seen,and via cut-out symbols in the top diffraction-generating microstructureand the diffraction-generating microstructure located beneath it theoptical effect of the underlying diffraction-generating microstructurecan be seen.
 6. A method according to claim 3 wherein three or morediffraction-generating microstructures are affixed on top of one anotherand, through some cut-out symbols in the top diffraction-generatingmicrostructure, the optical effect of the diffraction-generatingmicrostructure located beneath it can be seen, and via cut-out symbolsin the top diffraction-generating microstructure and thediffraction-generating microstructure located beneath it the opticaleffect of the underlying diffraction-generating microstructure can beseen.
 7. An article to which a security code has been applied by amethod comprising:applying a diffraction generating microstructure tothe article, in which diffraction-generating microstructurepersonification or identification symbols are cut out by means ofburning-in using a laser beam, wherein the said diffraction-generatingmicrostructure defines a top diffraction-generating microstructure, thatis glued to an underlying diffraction-generating microstructure which isaffixed to the article directly or via one or more otherdiffraction-generating microstructures, the symbols being cut out fromthe top diffraction generating microstructure in such a size so that theoptical effect of the underlying diffraction-generating microstructurebecomes visible and/or detectable.
 8. An article according to claim 7wherein the said symbols are made before the top diffraction-generatingmicrostructure is affixed to the underlying diffraction-generatingmicrostructure.
 9. An article according to claim 7 wherein the saidsymbols are burned in by means of laser beams after affixing the topdiffraction-generating microstructure, without the underlyingdiffraction-generating microstructure being damaged.
 10. An articleaccording to claim 7 wherein three or more diffraction-generatingmicrostructures are affixed on top of one another and, through somecut-out symbols in the top diffraction-generating microstructure, theoptical effect of the diffraction-generating microstructure locatedbeneath it can be seen, and via cut-out symbols in the topdiffraction-generating microstructure and the diffraction-generatingmicrostructure located beneath it the optical effect of the underlyingdiffraction-generating microstructure can be seen.